Effect of waveguide optical parameters on alignment tolerances for fibre attachment

The demands of device design often result in devices with output optical parameters significantly different to standard single mode fibre. This results in an increase in coupling loss and a greater sensitivity to misalignment even when the fibre parameters are modified to match the device. In this paper we look at the effect of the optical parameters of a rectangular planar waveguide (height, width and refractive index difference) on the coupling loss and alignment tolerance for fibre attachment. It is shown that in the case of V-groove alignment of ribbon fibre (for example), where the height deviation of fibre cores can be significantly greater than the pitch deviation and there is a channel to channel variation in bond line thickness, this can lead to significant channel to channel variation in coupling loss.